Bibcode
Marks, M.; Martín, E. L.; Béjar, V. J. S.; Lodieu, N.; Kroupa, P.; Manjavacas, E.; Thies, I.; Rebolo López, R.; Velasco, S.
Bibliographical reference
Astronomy and Astrophysics, Volume 605, id.A11, 11 pp.
Advertised on:
8
2017
Journal
Citations
7
Refereed citations
7
Description
Context. One of the key questions of the star formation problem is
whether brown dwarfs (BDs) form in the manner of stars directly from the
gravitational collapse of a molecular cloud core (star-like) or whether
BDs and some very low-mass stars (VLMSs) constitute a separate
population that forms alongside stars comparable to the population of
planets, for example through circumstellar disk (peripheral)
fragmentation. Aims: For young stars in Taurus-Auriga the binary
fraction has been shown to be large with little dependence on primary
mass above ≈ 0.2 M⊙, while for BDs the binary fraction
is < 10%. Here we investigate a case in which BDs in Taurus formed
dominantly, but not exclusively, through peripheral fragmentation, which
naturally results in small binary fractions. The decline of the binary
frequency in the transition region between star-like formation and
peripheral formation is modelled. Methods: We employed a
dynamical population synthesis model in which stellar binary formation
is universal with a large binary fraction close to unity. Peripheral
objects form separately in circumstellar disks with a distinctive
initial mass function (IMF), their own orbital parameter distributions
for binaries, and small binary fractions, according to observations and
expectations from smoothed particle hydrodynamics (SPH) and grid-based
computations. A small amount of dynamical processing of the stellar
component was accounted for as appropriate for the low-density
Taurus-Auriga embedded clusters. Results: The binary fraction
declines strongly in the transition region between star-like and
peripheral formation, exhibiting characteristic features. The location
of these features and the steepness of this trend depend on the mass
limits for star-like and peripheral formation. Such a trend might be
unique to low density regions, such as Taurus, which host binary
populations that are largely unprocessed dynamically in which the binary
fraction is large for stars down to M-dwarfs and small for BDs.
Conclusions: The existence of a strong decline in the binary fraction -
primary mass diagram will become verifiable in future surveys on BD and
VLMS binarity in the Taurus-Auriga star-forming region. The binary
fraction - primary mass diagram is a diagnostic of the (non-)continuity
of star formation along the mass scale, the separateness of the stellar
and BD populations, and the dominant formation channel for BDs and BD
binaries in regions of low stellar density hosting dynamically
unprocessed populations.
Related projects
Very Low Mass Stars, Brown Dwarfs and Planets
Our goal is to study the processes that lead to the formation of low mass stars, brown dwarfs and planets and to characterize the physical properties of these objects in various evolutionary stages. Low mass stars and brown dwarfs are likely the most numerous type of objects in our Galaxy but due to their low intrinsic luminosity they are not so
Rafael
Rebolo López
Exoplanets and Astrobiology
The search for life in the universe has been driven by recent discoveries of planets around other stars (known as exoplanets), becoming one of the most active fields in modern astrophysics. The growing number of new exoplanets discovered in recent years and the recent advance on the study of their atmospheres are not only providing new valuable
Enric
Pallé Bago